Search

We studied the ionized gas in the inner region ($\sim680\times470$ pc$^2$) of the galaxy NGC 6868 using Gemini/GMOS integral field unit observations. Channel maps reveal complex kinematics and morphology, indicating multiple processes at work in NGC 6868. Through emission-line fitting, we identified two ubiquitous components in our data: a narrow ($\sigma\sim110$ km s$^{-1}$) tracing an ionized gas disc and a broad component ($\sigma\sim300$ km s$^{-1}$) mainly associated with inflowing/outflowing gas. The derived V-band reddening shows a spatial distribution consistent with that obtained from stellar population synthesis, although with generally higher values. For the first time, we measured the electron temperature in NGC 6868, finding values ranging from $\sim 14000$ K in the central region to $\gtrsim20000$ K with an outward increasing temperature gradient. The electron density map exhibits an inverse relationship, with central values reaching $N_e\sim4000$ cm$^{-3}$ for the broad component decreasing to $N_e\sim100$ cm$^{-3}$ towards the edges of the field of view. Using BPT diagrams, we found that all spaxels are consistent with both AGN and shock ionization. However, when this information is combined with our kinematic and temperature findings, and further supported by the WHAN diagram, we argue that an AGN is the dominant ionisation mechanism in the central region of NGC 6868, while the extended outer component is ionized by a combination of hot low-mass evolved stars and shocks. According to our findings, shocks play a significant role in the ionization balance of this galaxy., Comment: 16 pages, 16 figures, accepted for publication in MNRAS

Near-infrared long-slit spectroscopy has been used to study the stellar population (SP) of the low luminosity active galactic nuclei (AGN) and matched analogues (LLAMA) sample. To perform the SP fits we have employed the X-shooter simple stellar population models together with the \st\ code. Our main conclusions are: The star formation history of the AGNs is very complex, presenting many episodes of star formation during their lifetimes. In general, AGN hosts have higher fractions of intermediate-age SP (light-weighted mean ages, $_L\lesssim$ 4.5 Gyr) when compared with their analogues ($_L\lesssim$ 8.0 Gyr). AGN are more affected by reddening and require significant fractions of featureless continuum and hot dust components. The ratio between the AGN radiated energy and the gravitational potential energy of the molecular gas ($E_{Rad}$/$E_{PG}$) for the AGN is compared with the \maL\ and a possible anti-correlation is observed. This suggests that the AGN is affecting the star formation in these galaxies, in the sense that more energetic AGN (log$(E_{Rad}$/$E_{PG}) \gtrsim 3$) tend to host nuclear younger SP ($ _L \lesssim$4Gyr). We found that the recent ($t<$2~Gyr) returned (recycled) stellar mass is higher in AGN than in the controls. We also provide evidence that the mass loss of stars would be enough to feed the AGN, thus providing observational constraints for models that predict that AGN feeding is partially due to the recycled gas from dying stars., Comment: Accepted for publication in MNRAS

Emission-line studies in the active galactic nuclei (AGNs), particularly those utilizing high spatial resolution, provide the most accurate method to determine critical quantities of the central engine and of the gas a few tens of parsecs away. Using seeing-limited data with spectroscopy, we have explored the extended narrow-line region for a sample of active galactic nuclei (AGNs) with strong, forbidden emission lines that have high-ionization potentials (IP $\gtrsim$ 100 eV). We have studied the optical and near-infrared spectra for these AGNs, extracted and compared their spectral energy distributions, and put constraints on the physical conditions of the region producing the coronal lines. We have realized a novel black hole mass scaling relation with one such prominent coronal line - [Si VI] 1.963 microns, over the 10$^6$ - 10$^8$ M$_{\odot}$ interval, that suggests photoionization by the continuum produced by the accretion disk is the primary physical process at play here. We perform a detailed parameter space study to optimize the emission from these coronal lines in terms of fundamental black hole parameters and test predictions that can be used to measure the kinematics of the extended X-ray emission gas. With the successful launch and first light of the JWST, we are well-poised to refine our findings using the superb angular resolution of the telescope that will allow us to map the inner few parsecs to the central supermassive black holes. This opens up the study of the higher ionization lines that will be spatially resolved by JWST, expanding our sample to tens of hundreds of AGNs, and putting firmer constraints on the physical conditions in the coronal line region., Comment: 3 pages, 1 figure, version matches the published version in Proceedings of the XLV Annual Meeting of the Brazilian Astronomical Society

Variability studies have proven to be a powerful diagnostic tool for understanding the physics and properties of of Active Galactic Nuclei (AGNs). They provide insights into the spatial and temporal distribution of the emitting regions, the structure and dynamics of the accretion disk, and the properties of the central black hole. Here, we have analysed the K-band spectral variability of the Seyfert 1.9/2 galaxy NGC4388 spanning five epochs over a period of ten years. We have performed spectral synthesis of the nuclear region and found that the contribution of warm dust (T~800K) declined by 88% during these 10 years. In the same period, the [CaVIII] coronal line decreased 61%, whereas BrG emission declined 35%. For the HeI and H2, we did not detect any significant variation beyond their uncertainties. Based on the time span of these changes, we estimate that the region where the warm dust is produced is smaller than 0.6pc, which suggests that this spectral feature comes from the innermost part of the region sampled, directly from the AGN torus. On the other hand, the bulk of [CaVIII] is produced in the inner ~2pc and the nuclear BrG region is more extended, spanning a region larger than 3pc. Lastly, HeI and H2 are even more external, with most of the emission probably being produced in the host galaxy rather than in the AGN. This is the first spectroscopic variability study in the NIR for an AGN where the central source is not directly visible., Comment: Accepted in MNRAS. 8 pages, 3 figures

We use Gemini integral field unit observations to map the stellar population properties in the inner region ($\sim680\times470$ pc$^2$) of the galaxy NGC 6868. In order to understand the physical and chemical properties of the stellar content of this galaxy, we performed stellar population synthesis using the starlight code with the MILES simple stellar population models. We measured the absorption line indices Fe4383, Mg$_2$, Mg$_b$, Fe5270, Fe5335 for the whole FoV, and used them to derive Fe3 and [MgFe]'. These indices were used to derive [$\alpha$/Fe]. This galaxy is dominated by old metal-rich populations (12.6 Gyr; 1.0 and 1.6 Z$_\odot$) with a negative metallicity gradient. We also found a recent ($\sim63$ Myr) metal-rich (1.6 Z$_{\odot}$) residual star formation in the centre of the galaxy. A dust lane with a peak extinction in the V band of 0.65 mag is seen. No signs of ordered stellar motion are found and the stellar kinematics is dispersion dominated. All indices show a spatial profile varying significantly along the FoV. Mg$_2$ shows a shallow gradient, compatible with the occurrence of mergers in the past. Mg$_b$ and Fe3 profiles suggest different enrichment processes for these elements. We observe three distinct regions: for $R<100$pc and $R>220$pc, Mg$_2$, Mg$_b$ anti correlate with respect to Fe3 and [MgFe]', and for $100 \text{pc}

We use Gemini Near-Infrared Integral Field Spectrograph (NIFS) adaptive optics assisted data-cubes to map the stellar population of the inner few hundred parsecs of a sample of 18 nearby Seyfert galaxies. The near-infrared light is dominated by the contribution of young to intermediate old stellar populations, with light-weighted mean ages $_L\ \lesssim $ 1.5\,Gyr. Hot dust ($HD$) emission is centrally peaked (in the unresolved nucleus), but it is also needed to reproduce the continuum beyond the nucleus in nearly half of the sample. We have analysed the stellar population properties of the nuclear region and their relation with more global properties of the galaxies. We find a correlation between the X-ray luminosity and the contributions from the $HD$, featureless continuum $FC$ and reddening $A_V$. We attribute these correlations to the fact that all these properties are linked to the mass accretion rate to the active galactic nuclei (AGN). We also find a correlation of the bolometric luminosity $log(LBol_{obs})$ with the mass-weighted mean age of the stellar population, interpreted as due a delay between the formation of new stars and the triggering/feeding of the AGN. The gas reaching the supermassive black hole is probably originated from mass loss from the already somewhat evolved intermediate-age stellar population ($_L \lesssim $ 1.5\,Gyr). In summary, our results show that there is a significant fraction of young to intermediate age stellar populations in the inner few 100\,pc of active galaxies, suggesting that this region is facing a rejuvenation process in which the AGN, once triggered, precludes further star formation, in the sense that it can be associated with the lack of new star formation in the nuclear region., Comment: Accepted for publication in MNRAS

We map the optical and near-infrared (NIR) emission-line flux distributions and kinematics of the inner 320$\times$535pc$^2$ of the elliptical galaxy NGC1052. The integral field spectra were obtained with the Gemini Telescope using the GMOS-IFU and NIFS instruments, with angular resolutions of 0''88 and 0''1 in the optical and NIR, respectively. We detect five kinematic components: (1 and 2) Two spatially unresolved components, being a broad line region visible in H$\alpha$, with a FWHM of $\sim$3200km s$^{-1}$ and an intermediate-broad component seen in the [OIII]$\lambda \lambda$4959,5007 doublet; (3) an extended intermediate-width component with 280

We have used the Gemini Near-Infrared Integral Field Spectrograph (NIFS) in the J and K bands to map the distribution, excitation and kinematics of the ionized HII and warm molecular gas H$_2$, in the inner few 100 pc of 6 nearby active galaxies: NGC 788, Mrk 607, NGC 3227, NGC 3516, NGC 5506, NGC 5899. {For most galaxies, this is the first time that such maps have been obtained}. The ionized and H$_2$ gas show distinct kinematics: while the H$_2$ gas is mostly rotating in the galaxy plane with low velocity dispersion ($\sigma$), the ionized gas usually shows signatures of outflows associated with higher $\sigma$ values, most clearly seen in the [FeII] emission line. These two gas species also present distinct flux distributions: the H$_2$ is more uniformly spread over the whole galaxy plane, while the ionized gas is more concentrated around the nucleus and/or collimated along the ionization axis of its Active Galactic Nucleus (AGN), presenting a steeper gradient in the average surface mass density profile than the H$_2$ gas. The total HII masses cover the range $2\times10^5-2\times10^7$ M$_{\odot}$, with surface mass densities in the range 3-150 M$_{\odot}$ pc$^{-2}$, while for the warm H$_2$ the values are 10$^{3-4}$ times lower. We estimate that the available gas reservoir is at least $\approx$ 100 times more massive than needed to power the AGN. If this gas form new stars the star-formation rates, obtained from the Kennicutt-schmidt scalling relation, are in the range 1-260$\times$ 10$^{-3}$ M$_{\odot}$ yr$^{-1}$. But the gas will also - at least in part - be ejected in the form of the observed otflows.

We use the Gemini Near-Infrared Integral Field Spectrograph (NIFS) to map the stellar kinematics of the inner few hundred parsecs of a sample of 16 nearby Seyfert galaxies, at a spatial resolution of tens of parsecs and spectral resolution of 40 km/s. We find that the line-of-sight (LOS) velocity fields for most galaxies are well reproduced by rotating disk models. The kinematic position angle (PA) derived for the LOS velocity field is consistent with the large scale photometric PA. The residual velocities are correlated with the hard X-ray luminosity, suggesting that more luminous AGN have a larger impact in the surrounding stellar dynamics. The central velocity dispersion values are usually higher than the rotation velocity amplitude, what we attribute to the strong contribution of bulge kinematics in these inner regions. For 50% of the galaxies, we find an inverse correlation between the velocities and the $h_3$ Gauss-Hermitte moment, implying red wings in the blueshifted side and blue wings in the redshifted side of the velocity field, attributed to the movement of the bulge stars lagging the rotation. Two of the 16 galaxies (NGC 5899 and Mrk 1066) show an S-shape zero velocity line, attributed to the gravitational potential of a nuclear bar. Velocity dispersion maps show rings of low-$\sigma$ values (50-80 km/s) for 4 objects and "patches" of low-sigma for 6 galaxies at 150-250 pc from the nucleus, attributed to young/ intermediate age stellar populations., Comment: To be published in MNRAS